Many integrated optical processors, such as wavelength converters based on waveguides in PPLN (Periodically-Poled Lithium Niobate), are sensitive to polarization modes of the interacting optical signals. These PPLN wavelength converters can receive one or more input signals at different frequencies fs, and convert these signals to different frequencies fc with the help of energizing pump signals at frequencies fp. The frequency fc, of a converted signal is related to the frequency f, of its corresponding input signal and the frequency fp of its pump signal to provide a mechanism to define the frequencies of the converted signals from their input signals. However, PPLN wavelength converters are polarization sensitive and various physical effects in the processor can cause undesired results on an input signal of mixed polarization modes. These effects include dependence of the nonlinear coefficient and waveguide loss on the polarization of the interacting optical beams.
Optical systems designed to compensate for polarization sensitivity (e.g., systems that achieve “polarization diversity”) are known in the art. However, many of these systems utilize multiple discrete optical components that are not suitable for practical integration into monolithic optical processing systems.
On the other hand, the present invention provides for which polarization-insensitive integrated wavelength converters with components and designs which can be efficiently integrated into monolithic optical systems. Costs can be reduced and reliability can be increased, among other improvements.